Though looking a little ragged, Tropical Storm Isaac continued its trek west across the Caribbean early Friday on a course that should take it over parts of Hispaniola today and Cuba starting on Saturday.

It also remains on a projected track that would take it over the Keys early Monday and close to Tampa on Tuesday. Whether Isaac will reach hurricane strength by that time is uncertain.

However, the system could bring squally to severe weather to much of the state, starting Sunday. It could also disrupt the Republican National Convention, which starts on Monday.

On Thursday, Monroe County canceled school Monday as a precaution.

At 5 a.m. Friday, Isaac was about 165 miles south of Santo Domingo, Dominican Republic or about 230 miles southeast of Port Au Prince, Haiti. The storm was moving west-northwest at 15 mph with maximum sustained winds of 45 mph. A hurricane watch is in effect for Haiti.

Cuba issued a tropical storm watch Thursday afternoon, with a tropical storm warning for some provinces Thursday night. A tropical storm watch was in effect for the central Bahamas late Thursday.

The system is projected to hit the south shore of the Dominican Republic on Friday and Haiti and southeast Cuba on Saturday.

How much time the system spends over those land areas could determine how strong it will be when it arrives near Florida.

Isaac is expected to move into the Gulf of Mexico and strengthen only slightly by the time it approaches Tampa.

Still, the city would be on the storm's more vicious side and subjected to howling winds and torrential rains.

For now the Republican Convention is still on, although Gov. Rick Scott said it might be canceled if an evacuation is ordered for that area.

Scott said on Thursday morning that state officials are working with convention officials and monitoring Isaac's progress.

“Obviously we're hopeful it doesn't hit Florida, but we must take every precaution,” Scott said.

The convention is expected to draw 4,500 delegates, plus alternates, and tens of thousands of media and politicians to the Tampa area.

It's still is uncertain how much bad weather Isaac will produce over South Florida, but the National Weather Service in Miami said the region could see tropical storm conditions starting Sunday night and through the day on Monday.

"It’s still iffy, but you have the potential for tropical conditions," said weather specialist Bob Ebaugh.

Because heavy rainfall is possible, the South Florida Water Management District said it is taking steps to prevent flooding, including lowering canal levels in Miami-Dade and Collier counties.

Emergency managers urged South Florida residents to remain alert, in case the forecast takes a turn for the worse.

Johnson noted one wobble could bring the storm much closer to this region than currently forecast.

"Our citizens need to have their disaster plan in place, and they need to stay informed," he said.

Meanwhile, Tropical Storm Joyce emerged in the Central Atlantic on Thursday morning but weakened into a tropical depression by early Friday. The system, moving northwest at 14 miles per hour, has maximum sustained winds of 35 miles per hour.

Also, a new wave has rolled off the coast of Africa and could gradually develop.

The Food For The Poor headquarters in Port-au-Prince, Haiti is boarded up ahead of Tropical Storm Isaac on Thursday Aug. 23, 2012. Food For The Poor has positioned food and emergency supplies around the island.